Work sheet processing machines such as punch presses perform not only processing operations such as hole making and shape formation but also a processing operation of cutting product work sheets from a material work sheet by punching or the like. With importance attached to the processing efficiency of the work sheet processing machine, material work sheets of the same size are often used in spite of the different sizes or shapes of product work sheets that are to be cut from the material work sheet. Thus, depending on the type of the product work sheets, after the product work sheets are cut from the material work sheet, a redundant work sheet may remain which can still be processed into product work sheets. Such a sheet is conventionally disposed of as a waste material instead of being effectively utilized.
On the other hand, product work sheets are carried out from the work sheet processing machine by a work sheet conveying device (for example, the Unexamined Japanese Patent Application Publication (Tokkai) No. 2000-117374). The product work sheets are then stored in a work sheet cabinet (for example, the Unexamined Japanese Patent Application Publication (Tokkai-Hei) No. 5-306003) or loaded on a vehicle and transported to the next step. The redundant work sheet is not conveyed by the work sheet conveying device or stored in the work sheet cabinet.
As described above, in the prior art, the redundant work sheet is disposed of instead of being effectively utilized, resulting in the wasteful use of the material. Although the waste can be eliminated by cutting plural types of product work sheets from one material work sheet, this is difficult for the following reason. That is, in order to avoid increasing an intermediate stock and complicating a sorting operation, a processing schedule for the work sheet processing machine is basically specified such that the product work sheets are processed in the order in which the product work sheets need to be used during the subsequent steps. Thus, product work sheets of the same type or product work sheets to be used during the same step are necessarily processed consecutively, unavoidably generating redundant work sheets.
It is thus possible to temporarily store a redundant work sheet generated by the work sheet processing machine, in a different place and to bring the redundant work sheet back to the work sheet processing machine for use where the redundant work sheet can be utilized for the process. To achieve this, it is necessary to provide a device transporting the redundant work sheet and a facility in which the redundant work sheet is stored. However, the conventional technique does not provide such a device or a facility. It is convenient to utilize the work sheet conveying device and work sheet cabinet for product work sheets to convey and store redundant work sheets. However, this may affect the conveyance and storage of the product work sheets or result in confusion owing to the mixture of the product work sheets and redundant work sheets.
An object of the present invention is to provide a work sheet processing system that enable the effective utilization, without adverse effects on the operation of a work sheet processing machine or other peripheral devices, of a redundant work sheet corresponding to a material work sheet from which product work sheets have been cut, a part of the redundant work sheet being still capable of being processed into other product work sheets. Another object of the present invention is to allow the redundant work sheet to be efficiently carried out from and into the work sheet processing machine. Yet another object of the present invention is to provide a means for carrying in and out the redundant work sheet, the means having a simple configuration and allowing redundant work sheet to be reliably carried in and out.